Field of the Invention
This application relates to apparatuses and methods for maintaining alignment of cannulated shafts over slender guide structures, such as guide pins.
Description of the Related Art
It is conventional in orthopedics to use a drill or other driver tool equipped with a drill bit to modify bone and to deliver implants into a bone surface or cavity. A surgeon can use a simple technique to guide the advancement of the drill bit, such as simply visually confirming that the drill bit is advancing in a proper direction relative to the bone surface or cavity. Such simple techniques are adequate for gross alignment of the direction of advance of a drill bit but are inadequate where higher precision is desired.
A technique for improving guidance of a drill bit is to first place a rigid guide pin into the bone. In this technique, the drill bit has a hollow shaft that is placed over the guide pin. As a result, the inner surface of the shaft and the outer surface of the guide pin interact to reduce the range of directions of advance of the hollow shaft of the drill bit relative to the central longitudinal axis of the guide pin. While a guide pin can reduce the variability of the direction of advance of a drill bit relative to the bone, there is still the possibility that the shaft of the drill bit can be non-parallel to, or otherwise offset from, the guide pin. Also, the guide pin outside of the bone can be bent at an angle relative to the guide pin inserted in the bone thereby not guiding the drill bit along the originally intended direction of the guide pin. A further technique that can be used to correct for such misalignment involves the user re-positioning the drill bit in response to drag between the drill bit shaft and the guide pin. Greater drag indicates a larger angle between the pin and the drill bit shaft. This approach is user and experience dependent, and thus not very reliable or precise.
Complex systems exist for determining an angle of advance of a drill bit by sensing position in space. Such systems require electronics and software which increase the complexity and cost of the system and of procedures utilizing the systems.